There has been known a vehicle, such as an automobile, which is provided with a variety of actuators to actively control behaviors of the vehicle through the intermediary of the variety of actuators according to diverse state amounts of the vehicle or external environmental conditions as well as passively controlling (according to operations of operating devices performed by a driver) the behaviors of the vehicle in response to man-caused operations of the operating devices, such as a steering wheel, an accelerator (gas) pedal, a brake pedal, and a shift lever.
The present applicant has proposed in, for example, Japanese Unexamined Patent Application Publication No. 2000-302055 (hereinafter referred to as “patent document 1”), a technology for controlling the steering of a vehicle, which can be steered by actuators, such that the vehicle follows a desired course. The technology predicts a future lateral displacement of the vehicle with respect to a desired course determined on the basis of the information obtained by a CCD camera or the like. Further, a control input for controlling the steering of the vehicle is determined such that the lateral displacement and a temporal change amount of a steering angle are minimized as much as possible is determined. Then, the steering of the vehicle is performed through the intermediary of the actuators by the control input.
Furthermore, a control technique called “the model following method” has been disclosed in, for example, FIG. 6-99(a) on page 225 of “Automotive Engineering Handbook—Basics and Theory (Vol. 1)/The Society of Automotive Engineers of Japan (published on Jun. 15, 1992)” (hereinafter referred to as non-patent document 1)). According to the control technique, a steering angle of a steering wheel operated by a driver is input to a reference model for which steering response characteristics have been set beforehand, and a control input for a vehicle model is determined such that an output of the vehicle model follows an output of the reference model. Then, the control input of the vehicle model is input to the actual vehicle so as to cause the actual vehicle to follow the reference model.